const promise = new Promise((resolve, reject) => {
  setTimeout(() => {
    if (Math.random() < 0.5) {
      resolve('正常')
    } else {
      reject('异常')
    }
  }, 1000)
})

promise.then(
  res => {
    // 正常
    console.log(res)
  },
  res => {
    // 异常
    console.log(res)
  }
)
